regime that it would be a major incident, that if the assad regime were to use chemicals, it would be taking military steps against it. but there is no evident yet, according to u.s. officials here today, that that actually happened on tuesday. that incident, it could have been some form of noxious gas that was used for crowd control by the regime. but the president said in a joint news conference with prime minister netanyahu yesterday that there's absolutely no evidence and he completely rejects the regime's contentions that it was the opposition that used those chemicals. >> i am deeply skeptical of any claim that, in fact, it was the opposition that used chemical weapons. the broader point is that once we establish the facts, i have made clear that the use of chemical weapons is a game changer. >> reporter: the u.n. is investigating the incident. and congressional sources say that the intelligence committees have been briefed and that the administration has full authority to get militarily involved if chemical weapons, if there's any proof of chemical weapons. and in fact, that wo